The present invention relates to an immunoassay system which uses anti-idiotype antibodies in place of antigen and which is therefore antigen-independent. The invention also relates to a method for generating anti-idiotype antibodies.
The competitive immunoassay has classically been used to determine the presence of an antigen in a sample by measuring the inhibition of formation of a standard antigen-antibody complex, one of which is typically bound and the other of which is typically labeled, by free antigen in the sample. In addition, a typical quantitative immunoassay kit will include a standardized sample of pure antigen so that a reference solution can be run together with the sample to minimize sampling errors and to assure precision. In many cases, the antigen may be quite difficult to isolate and purify, and may also be of limited stability.
Antibodies which recognize the hypervariable or idiotype region of an antibody have been implicated in the regulation of the immune system. They are known as anti-idiotypes (a-Id). Thus, an antibody which specifically binds a particular antigen (a-Ag) will also specifically bind its complementary a-Id. It has been suggested that a complementary a-Ag/a-Id antibody pair could be used in a competitive immunoassay wherein antigen in the sample would compete with a-Id for labeled a-Ag, the extent of a-Id/a-Ag complex formation being inversely proportional to the antigen concentration in the sample. See, e.g., Potocnjak et al, Science, 215, 1637 (1982); and Mitchell et al, Aust. J. Exp. Biol. Med. Sci., 61, 27 (1983). However, there has been no suggestion of using a-Id antibodies as a substitute for purified antigen for the reference component of a competitive immunoassay kit, which would permit accurate, quantitative immunoassays which are antigen-independent.
Typically, a-Ids are produced by challenging an animal with the a-Ag, in an antigenically active form, and recovering antiserum, or recovering lymphocytes and fusing them with myeloma cells to form hybridomas. There is no suggestion of using lymphocytes from an animal in which a hybridoma tumor is growing and secreting monoclonal a-Ags, as a source of a-Ids.